Bun has transitioned to Rust with over a million lines of code and 6,755 commits, primarily generated by Claude Code agents in nine days. The previous Zig implementation has been removed following Anthropic's acquisition of Bun in December.

Bun has achieved a 100x speed increase by rewriting Git in the Zig programming language and integrating it into its runtime. This enhancement significantly improves performance for developers using Bun.